1. Field of the Invention
The present invention relates to an edit point decoding method suitable for use with moving picture image signals, sound signals, etc. edited and recorded in a random access recording medium such as a magneto-optic disc, a decoding player adapted to read a recording medium in which such edited signals are recorded, and a recording medium having such edited signals recorded therein.
2. Description of Related Art
Assume here that, for example, a moving picture image signal, sound signal, etc. having a length of time of 1 hour, 2 minutes and 3 seconds and consisting of 4 frames are recorded in a fresh recording medium (random access or accessible recording medium such as magneto-optic disc or the like; it will be referred to simply as xe2x80x9cdiscxe2x80x9d hereafter). The recorded data are laid on the disc as shown in FIGS. 1A and 1B. FIG. 1A shows three recording areas A, B and C on the disc. The recording areas are contiguous like a line extending from the innermost perimeter of the disc to the outermost perimeter. FIG. 1B shows only one of the three areas, say, the area B.
As mentioned above, the entire disc consists of the three areas A, B and C. The area A is the innermost area on the disc. The areas B and C extend from the area A toward the outermost perimeter of the disc.
The area A shown in FIG. 1A has recorded therein an information for managing the information recorded on the disc, namely, a so-called xe2x80x9cTOC (Table Of Contents)xe2x80x9d. The TOC includes at least xe2x80x9centriesxe2x80x9d and a plurality of xe2x80x9careas for describing the entriesxe2x80x9d. Each of the entries specifies at least information such as xe2x80x9cstart addressxe2x80x9d, xe2x80x9cend addressxe2x80x9d, xe2x80x9cstart time codexe2x80x9d, xe2x80x9cend time codexe2x80x9d, and xe2x80x9cnext entryxe2x80x9d.
The xe2x80x9cstart addressxe2x80x9d has described therein a leading address of an area managed by the entries. The leading address is an address determined by a physical medium, or an address of a file system, configured on a physical address, as the case may be.
The xe2x80x9cend addressxe2x80x9d has described therein an end address of the area managed by an entry.
The xe2x80x9cstart time codexe2x80x9d has described therein a start time code of a moving picture image data recorded in the area managed by the entries.
The xe2x80x9cend time codexe2x80x9d has described therein an end time code of a moving picture image data recorded in the area managed by the entries.
The xe2x80x9cnext entryxe2x80x9d has described therein a number for a further entry, if any, to be reproduced during disc reading. If there exists no next entry to be reproduced, xe2x80x9cNullxe2x80x9d is described in the xe2x80x9cnext entryxe2x80x9d.
The TOC in the following description is configured on the assumption that the time codes in the entries are continuous. On any other assumption, however, the TOC will be configured otherwise than herein.
There is recorded in the area B in FIGS. 1A and 1B, the moving picture image information having a length of time of 1 hour, 2 minutes and 3 seconds and consisting of 4 frames. It is assumed here that the moving picture image information includes an MPEG2 Video signal and an MPEG2 Audio signal resulted from time-division multiplexing with a Program Stream of a so-called MPEG2 system, for example. However, the essentials of the video and audio signals will not vary even if any other time-division multiplexing method and video and audio coding methods are adopted for generation of the video and audio signals. The MPEG referred to herein stands for the Moving Picture Experts Group being the Image Coding group of the ISO/IEC JTC/SC29 (International Organization for Standardization/International Electrotechnical Commission, Joint Technical Committee 1/Sub Committee 29). The MPEG1 standard include ISO 11172, and the MPEG2 standard includes ISO 13818. In these international standards, ISO 11172-1 and ISO 13818-1 are included in the item of system multiplexing, ISO 11172-2 and ISO 13818-2 are included in the item of video coding, and ISO 11172-3 and ISO 13818-2 are included in the item of audio coding.
In FIG. 1A, the area C has nothing recorded therein.
The following information are recorded in the area A (TOC). In this condition, the TOC has one entry.
Entries=1
Contents of entry 0
Start address=addr0
End address=addr1
Start time code=0:00:00:00 (as in FIG. 1B)
End time code=1:02:03:04 (as in FIG. 1B)
Next entry=None
Contents of entry 1 (same as above)
Null information
Currently, the area B in FIGS. 1A and 1B has recorded therein the MPEG stream between 0 hour, 0 minute, 0 second, and 0 frame (0:00:00:00) indicated with the start time code and 1 hour, 2 minute, 3 seconds and 4 frames (1:02:03:04) indicated with the end time code. Also, the area C has nothing recorded therein as shown in FIG. 1A.
The editing procedure using a disc having the above-mentioned video and audio information recorded therein will be described herebelow:
As one example of the editing procedure, a partial deletion of the data recorded in the disc as mentioned above will be explained with reference to FIGS. 3A and 3B As shown, a part between 0 hour, 0 minute, 0 second and 0 frame (0:00:00:00) and 0 hour, 20 minutes, 30 seconds and 4 frames (0:20:30:04), and a part between 0 hour, 40 minutes, 50 seconds and 6 frames (0:40:50:06) and 1 hour, 2 minutes, 3 seconds and 4 frames (1:02:03:04), are to be left on the disc. That is, a part between 0 hour 20 minutes, 30 seconds and 5 frames (0:20:30:05) and 0 hour, 40 minutes, 50 seconds and 5 frames (0:40:50:05), is to be deleted.
An edition of a data, say, a partial deletion of the data, as in the above will lead to two different results, depending upon how the stream is arranged after the data edition.
That is to say, the partial data deletion can be done with two techniques. The data is forwarded or not for the deleted part at the time of editing. In other words, skip has to be done or not over the deleted part at the time of reproducing the edited data. More particularly, after the data is partially deleted, a subsequent data is forwarded for a blank part resulted from the deletion (which will be called xe2x80x9cfirst editing methodxe2x80x9d hereafter), and the stream position is reserved just with the unnecessary part deleted (which will be called xe2x80x9csecond editing methodxe2x80x9d hereafter). Thus, the edition will lead to the two different results of edition depending upon the adopted editing method (arrangement of the stream). However, the edit points in the results are little different from each other. This is because both the techniques of edition have some problems which will not be further described herein.
First, the result of the first editing method (the subsequent data forwarded for the blank part after the deletion of an unnecessary part) adopted as the editing procedure (arrangement of data streams) will be described in detail below:
FIGS. 3A and 3B schematically show the result of edition from the first editing method. FIG. 3A shows three recording areas A, B and C on the disc. The recording areas A, B and C are contiguous like a line extending from the innermost perimeter of the disc to the outermost perimeter. FIG. 3B shows only one of the three areas, say, the area B in which the data is forwarded for the deleted unnecessary part.
In the example shown in FIGS. 3A and 3B, a part between 0 hour, 20 minutes, 30 seconds and 5 frames (0:20:30:05) being a frame next to 0 hour, 20 minute, 30 second and 4 frames (0:20:30:04) in FIG. 2 and 0 hour, 40 minutes, 50 seconds and 5 frames (0:40:50:05) being a frame preceding 0 hour, 40 minutes, 50 seconds and 6 frames (0:40:50:06) in FIG. 2 is deleted and the subsequent data is forward to the trailing end of the former data.
By forwarding the subsequent data for the deleted unnecessary part as in the example shown in FIGS. 3A and 3B, an area corresponding to the deleted part will be a new area in which data can be recorded , thus, the area C will be expanded correspondingly.
Through the edition as in FIGS. 3A and 3B is done, the following information will be recorded in the TOC. In this condition, the TOC includes two entries:
Entries=2
Contents of entry 0
Start address=addr0
End address=addr2
Start time code=
End time code=0:20:30:04
Next entry=1
Contents of entry 1
Start address addr2+1
End address=addr3
Start time code=0:40:50:06
End time code=1:02:03:04
Next entry=None
Contents of entry 2 (same as above)
Null information
In this first editing method, it is necessary to forward data for only the deleted part. However, it is not necessary to skip over the unnecessary part in a subsequent reproduction.
To implement the forwarding in the first editing method, however, the part to be forwarded, say, a part between 0 hour, 40 minutes, 50 seconds and 6 frames (0:40:50:06) and 1 hour, 2 minutes, 3 seconds and 4 frames (1:02:03:04) has to be saved once in any other recording medium (for example, hard disc) and recorded again as shown in FIG. 2, which is not practical.
On the other hand, when the second editing method (the stream position is kept unchanged with only the unnecessary part deleted) is adopted, it is not required to save the data into the other recording medium temporarily and re-recorded. FIGS. 4A and 4B schematically show the results of an using the second editing method. As seen, FIG. 4A shows three recording areas A, B and C on the disc. The recording areas A, B and C are contiguous like a line extending from the innermost perimeter of the disc to the outermost perimeter. FIG. 4B shows only the stream whose position remains unchanged just with the unnecessary part deleted.
In the example shown in FIGS. 4A and 4B, a part between 0 hour, 20 minutes, 30 seconds and 5 frames (0:20:30:05) being a next frame to 0 hour, 20 minute, 30 second and 4 frames (0:20:30:04) in FIG. 2 and 0 hour, 40 minutes, 50 seconds and 5 frames (0:40:50:05) being a frame preceding 0 hour, 40 minutes, 50 seconds and 6 frames (0:40:50:06) in FIG. 2 is left deleted while the stream position is kept unchanged.
To reproduce the edited data by the second editing method as in FIGS. 4A and 4B, a continuous reproduction by entering the TOC is designated. More particularly, the TOC edited as in the example shown in FIGS. 4A and 4B will have the following information recorded therein. In this condition, the TOC includes two entries as follows:
Entries=2
Contents of entry 0
Start address=addr0
End address=addr2
Start time code=0:00:00:00
End time code=0:20:30:04
Next entry=1
Contents of entry 1
Start address=addr4
End address=addr1
Start time code=0:40:50:06
End time code=1:02:03:04
Next entry=None
Contents of entry 2 (same as above)
Null information
In this second editing method, any thing (such as temporal save, forwarding, etc. as in the first editing method) may not be done at the time of the edition but it is necessary to skip over the unnecessary part at the time of reproduction.
Seemingly, the data edited by the first editing method as previously mentioned can be subsequently reproduced with no seam between the data on the recording medium (disc) by decoding it as it is read from the recording medium.
Also, it seems that the result of edition from the second editing method can be subsequently reproduced with no seam between the streams by skipping over the unnecessary part of the data and connecting to each other the data streams before and after the skipped part. Further, seemingly the connection between the streams before and after the unnecessary part over which the skip is made can theoretically be achieved just by selecting a sector address to be decoded.
For the reproduction, however, the inherently contiguous streams are disconnected from each other and another stream is connected. Therefore, if it is intended to reproduce a data whose redundancy is eliminated by using the continuity specified particularly in the MPEG and the like, the streams cannot easily be connected to each other at a desired point of connection. That is, an MPEG data is compression-coded using a signal before or a signal after the MPEG data, or both, and thus the compression-coded data cannot be decoded simply by connecting the two streams to each other.
The problems possibly taking place when an MPEG stream is subjected to an edition such as the second editing method in which skipping must be done at the time of reproduction, will be described below. The description will also true for the first editing method.
First, the MPEG will be briefly described and then the problems will be described.
The MPEG provides three types of coding such as I, B and P pictures for efficient coding of an image and for random access to the encoded image. The pictures referred to herebelow are ones whose frames or fields composing an moving picture image are encoded.
The I picture is a completely encoded one in the above-mentioned frame and encoded independently of other frames, Therefore, the I picture is used as an entry point for restoration of a random access or an error.
The P picture is predicted from an earlier I or P picture in a mode in which a forward prediction coding is done. Therefore, for decoding a P picture, the earlier I or P picture must have been decoded.
The B picture is a development of a P picture. It is predicted forward, backward or in both directions from an earlier and later I or P picture. Therefore, to decode a B picture, an I or P picture before and after the B picture, respectively, should have been decoded.
Generally, in the common applications, I, B and P pictures are used in combination to achieve a random access and a high efficiency of coding.
FIGS. 5A and 5B show together an example of such combination of I, B and P pictures. In FIG. 5A, the above-mentioned I, B and P pictures are arranged in the displaying order. The arrow d in this Figure indicates a predicting direction. To decode the B picture for display, for example, I or P pictures displayed before and after the B picture in a time sequence should be decoded prior to the decoding of the B picture. More particularly, for a displaying order as shown in FIG. 5A, for example, to decode an image of the picture B5, at least the pictures I0, P2, P4 and P6 should have been decoded. That is to say, the picture P2 is predicted from I0, P4 is from P2, P6 is from 10, and B5 is from P4 and P6. Thus, for decoding the B5 picture, the pictures I0, P2, P4 and P6 should previously been decoded. For this purpose, the pictures are rearranged in an order of I0, P2, B1, P4, B3, . . .  in the coding stream as shown in FIG. 5B. In other words, the medium (disc) has recorded thereon an encoded stream in the order of pictures shown in FIG. 5B. Therefore, for reproduction of this disc and display an image on a display unit, each picture is decoded from the encoded stream reproduced from the disc in the order shown in FIG. 5B, and rearranged as shown in FIG. 5A.
For the audio data coding, compression techniques such as the so-called AC-3 (ATSC standard Doc. A/52, 20 Dec. 1995) are available in addition to the aforementioned MPEG. In all these compression techniques, a predetermined number of sampled data is handled as a unit for coding as well as for decoding.
Generally, the period of decoding an audio frame being a unit of audio decoding has no coincidence with that of decoding a picture resulted from coding of video data. FIGS. 6A and 6B show time sequences of video decoding and audio decoding, respectively. FIG. 6A shows constitutive units (pictures) of an encoded data of an image, and a time point TP at which display of each picture is started, and FIG. 6B shows constitutive units (audio frames) of an encoded data of a sound, and a time point TA of each audio frame. As seen from FIGS. 6A and 6B, the period of decoding the audio frame does not coincide with that of decoding the picture.
In the recent standardized and commercially available products such as video CD and DVD (digital video disc), an image is encoded according to the aforementioned MPEG and a sound is encoded according to the MPEG or AC-3. Such data are time-division multiplexed as in the MPEG standard for recording on a disc.
Now, recording in a medium such as a disc of an image data encoded as in the aforementioned MPEG standard and edited by the aforementioned second editing method, will be discussed below. In this recording, the pictures are laid as shown in FIG. 7A taking in consideration the efficiency of coding and random accessibility. In the example shown in FIG. 7A, of the video stream resulted from the edition by the second technique, a stream down to a P picture indicated at a point SA is reproduced, skip is made over the subsequent pictures, and the reproduction of the stream is resumed at a B picture (B3) indicated at a point SB. Note that the skip start point corresponds to the edit out point and skip end point corresponds to the edit-in point.
To decode the B picture (picture B3 in the example in FIG. 7B), however, the I or P picture before the picture B3 (at least each of the pictures I0, P2 and P4 in the example in FIG. 7A) should have been decoded. In the above example, the video signal is encoded as in the MPEG, however, it should be appreciated that even in a prediction-coding technique in which the inter-image correlation is used to determine and encode a difference between the images, the reproduction will possibly be discontinued at the connections between the streams for the above-mentioned reasons.
On the other hand, in the aforementioned MPEG or AC-3 in which a predetermined number of sampled data is used as a unit of coding in the audio coding technique, the period of decoding a video signal is not always coincident with that of decoding an audio signal. Thus, if a continuous reproduction of a video signal is preferentially done while two streams are connected to each other at an edit point, a blank section takes place in which an audio signal is not generated, as will be described below. The blank section will be referred to as xe2x80x9caudio gapxe2x80x9d hereafter.
FIGS. 8B and 8C show time sequences of encoded video and audio data, respectively, recorded in a disc.
A following procedure will be described herebelow. That is, the video signal in FIG. 8B down to a picture (end of a picture VA in the example in FIG. 8D, corresponding to an edit-out point), is reproduced and displayed, and then the reproduction and decoding are resumed from another picture shown in FIG. 8F (top of a picture VC in the example in FIG. 8F, corresponding to an edit-in point) via skip over data as timed as shown in FIG. 8A.
For decoding of an audio signal at (corresponding to) the connection between such video signal streams, audio frames down to an audio frame AB corresponding to the picture VA will be decoded as shown in FIG. 8E, and then reproduction and decoding be restarted from an audio frame AD corresponding to the picture VC as in FIG. 8G.
The video and audio signals have to be reproduced synchronously with each other. To this end, the phase difference of the audio signal with respect to the video signal, say, the phase difference between picture display start time and audio frame start time, should not be varied due to the edition.
However, if a continuous display is tried by preferentially connecting the video streams to each other at the stream connection during an edition as shown in FIG. 8H, namely, by connecting to each other the picture VA before the skip and the picture VC after the skip to each other, there will occur a time duration (audio gap AG) in which no audio data exists in the audio stream as shown in FIG. 8I, resulting in an impossibility of continuous audio reproduction.
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a method and player for decoding edit points, and a recording medium, in which a good connection can be achieved between data streams when connecting to each other the data streams edited with their redundancy removed based on the data continuity as in the MPEG, etc. and recorded in the recording medium, interrupting once the stream read from the recording medium and connecting it to another data stream.
The above object can be accomplished by providing a method and player for reading an encoded data row consisting of a succession of predetermined encoded data groups including a plurality of frames, and a reproduction control information including information on an edit-out point and edit-in point, respectively, for use in data edition, from a random-accessible recording medium having recorded therein at least the encoded data row and reproduction control information, and decoding the read encoded data row based on the reproduction control information, in which before a time for output of the edit-out point is reached, a leading position of a first section consisting of encoded data row before the edit-out point is calculated based on the reproduction control information and the encoded data row in the first section is decoded and stored; when an output time for the leading position of the first section is reached, the encoded data row in a second section between the edit-out point and an edit-in point is decoded while the decoded data from the leading position of the first section is being output; and when a time for output of the edit-in point is reached, the encoded data row following the second section is decoded and output.
Also, the above object can be accomplished by providing a method and player for reading an encoded data row consisting of a succession of predetermined encoded data groups comprising a plurality of frames, and a reproduction control information including information on an edit-out point and edit-in point, respectively, for use in data edition, from a random-accessible recording medium having recorded therein at least the encoded data row and reproduction control information, and decoding the read encoded data row based on the reproduction control information, in which before a time for output of the edit-out point is reached, a leading position of a first section consisting of encoded data row before the edit-out point is calculated based on the reproduction control information and the encoded data row in the first section are decoded and stored; when an output time for the leading position of the first section is reached, the decoded data from the leading position of the first section is output while being faded out and the encoded data row in a second section between the edit-out point and an edit-in point is decoded and faded in; and when a time for output of the edit-in point is reached, the encoded data row following the second section is decoded and output.
According to another aspect of the present invention, the encoded data in the first section, to be doubly decoded, is decoded and stored before the edit point is reached, the encoded data in the second section between the edit-out point and the edit-in point is decoded while the decoded data in the first section is being output, and the decoded data in the second section is used to enable the decoding of data after the edit-in point.
The above object can also be accomplished by providing a recording medium having recorded therein signals produced through a produced in which before a time for output of an edit-out point is reached, a leading position of a first section consisting of encoded data row before the edit-out point is determined based on a reproduction control information recorded therein and an encoded data row in the first section is decoded and stored; when an output time for the leading position of the first section is reached, the encoded data row in a second section between the edit-out point and an edit-in point is decoded while the decoded data from the leading position of the first section is being output; and when a time for output of the edit-in point is reached, the encoded data row following the second section is decoded.
According to another aspect of the present invention, there is provided a recording medium having recorded therein signals produced through a procedure in which before a time for output of an edit-out point is reached, a leading position of a first section consisting of encoded data row before the edit-out point is calculated based on the reproduction control information and the encoded data row in the first section are decoded and stored; when an output time for the leading position of the first section is reached, the decoded data from the leading position of the first section is output while being faded out and the encoded data row in a second section between the edit-out point and an edit-in point is decoded and faded in; and when a time for output of the edit-in point is reached, the encoded data row following the second section is decoded.